There are conventionally well-known flow regulating devices used in a fluid supplying line for mixing together a plurality of different liquid chemicals, for accurately regulating the flow rate of pure water or the like used in a process of manufacturing products or the like. Such a flow regulating device is also generally referred to as “regulator”. As a flow regulating device used for this type of application, there is known a device configured as disclosed in PTL 1 indicated below, for example.
In the flow regulating device disclosed in PTL 1, the air pressure of air introduced to a pressure chamber is applied to a first diaphragm. The pressure applied to the first diaphragm is transmitted to a second diaphragm through an annular curved portion provided therebetween. A valve element is fixed to the second diaphragm, and the air pressure in the pressure chamber causes a force to be exerted on the valve element in a direction to bring the valve element away from a valve seat. As the valve element is urged by an urging force from a spring in a direction to bring the valve element into contact with the valve seat, the position of the valve element with regard to the valve seat is adjusted by adjusting the air pressure in the pressure chamber.